Systems and methods for obtaining low-angle circumferential optical access to the eye

ABSTRACT

A system for obtaining low-angle circumferential optical access to an eye of a subject. The system includes a light source to generate a beam of light; a beam steering mechanism to steer the beam of light a focusing lens to focus the beam of light; and a contact lens to direct the beam of light into the eye of the subject, the contact lens including a tapered reflective surface to direct the beam of light into the eye of the subject.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/372,599, filed Jul. 16, 2014, which is a national stage filing under35 U.S.C. 371 of International Patent Application No. PCT/US2013/022913,filed Jan. 24, 2013, which claims the benefit of priority to U.S.Provisional Patent Application No. 61/590,052 filed Jan. 24, 2012, thecontents of which are incorporated herein by reference in itsentireties.

GOVERNMENT SUPPORT

This invention was made with government support under Grant Nos.:K23-EY021522, R21-EY020001, and K12-EY016333 awarded by the NationalInstitutes of Health. The government has certain rights in theinvention.

BACKGROUND

The present invention relates to methods and systems for obtaininglow-angle circumferential optical access to the eye.

Resistance in the ocular pathway results in elevated intraocularpressure (IOP), one of the most important risk factors for thedevelopment of vision-threatening glaucomatous changes. All currentglaucoma therapeutics lower IOP to prevent further neuronal death fromthis blinding disease.

Many of the clinically most vulnerable elements of the outflow pathway(trabecular meshwork, Canal of Schlemm, collector channels, and otherdistal structures) cannot be imaged using conventional medical imagingmodalities. These elements cannot be imaged with routine clinicalultrasound, computed tomography (CT) or magnetic resonance imaging (MRI)because the structures are too small (submillimeter) to be resolved withthese techniques. These elements cannot be imaged using standard opticalmicroscopy and can only be imaged in a limited fashion with opticalcoherence tomography (OCT) from the outside of the eye because they arelocated behind the translucent sclera, which completely obscuresstandard microscopy and substantially reduces the resolution andsignal-to-noise ratio of standard anterior segment OCT. These elementscannot be readily imaged from inside the eye because the index mis-matchat the air-cornea interface renders this angle region opticallyinaccessible from outside the unaltered eye, since any light reflectedfrom the angle region toward the cornea is totally internally reflectedat the air-cornea interface. As a result, diagnostics for the outflowpathway in vivo have been limited. Moreover, surgical therapeutics forthe outflow pathway in vivo have also been limited to large scaleinvasive techniques or restricted use of thermal lasers.

With reference to diagnostics, two techniques have been used clinicallyto evaluate the outflow pathway: tonography and conventional gonioscopy.Tonography involves the continuous measurement of the intraocularpressure over the course of minutes in response to a deforming weightplaced on the eye. Due to challenges with both the patient interface andthe technical difficulty of this test, tonography is currently rarelyused in the clinical setting. In contrast, gonioscopy involves theplacement of a special contact lens on the eye to directly visualize theentrance of the outflow pathway from the inside of the eye, and remainsa standard component of the glaucoma exam. However, visualizing only theentrance of the outflow pathway informs one only of the patency of theentrance—to distinguish between “open” or “closed” angle glaucomas. Nofurther information about the remainder of the outflow pathway beyondthe entrance (such as the trabecular meshwork and Schlemm's canal) isobtained because conventional gonioscopy does not allow forvisualization below the tissue surface. These internal structures arethe postulated actual sites of outflow resistance.

To view the entire extent of the outflow pathway, a tomographic imagingtechnique is required, preferably to view the critical structuresdirectly from inside the eye. Optical coherence tomography (OCT) is anon-invasive, micrometer resolution optical imaging technique that hasbeen successfully used in medicine to produce cross-sectional in vivoimages of a variety of tissues. In ophthalmology, OCT has become anaccepted clinical standard technique for imaging of retinal pathology.OCT is also routinely used for imaging the anterior segment, includingthe irido-corneal angle in the region of the trabecular meshwork fromthe outside, in which it is limited to providing gross anatomical viewsof those structures. The shortcomings of conventional anterior segmentOCT for imaging the ocular outflow pathway from outside the eye includeloss of signal and resolution by imaging externally through theoptically translucent corneal-scleral limbus, and the ability to onlymeasure selected angular location (typically temporal and nasal)limiting complete circumferential analysis. Histologically, the outflowpathway has been shown to vary circumferentially, and limited samplingmay not identify the pathologic areas.

To overcome these issues and to maximize the imaging capabilities of OCTfor this anatomical region, light would ideally be directed through theoptically clear cornea into the internal entrance of the outflow pathwayand scanned circumferentially. However, due to the large refractiveindex change between the corneal surface and the surrounding air, theirido-corneal angle is optically isolated (as a result of total internalreflection), making optical imaging of this area challenging.

As previously described, surgical therapeutics for the ocular outflowpathway in vivo have been limited to large scale invasive techniques orrestricted use of thermal lasers. Large scale invasive techniques referto “scalpel surgeries.” In these techniques, the surgeon utilizes ablade to open the ocular outflow pathway. This can be done externally asin trabeculectomy (a punch is used to locally “punch out” the entireoutflow pathway in a select region), canaloplasty (an opening is createdin the outflow pathway and then a catheter is driven circumferentiallyaround the entire pathway), among other procedures. Internal techniquesare also available such as in goniotomy, in which a blade is insertedinto the anterior chamber and the internal opening of the outflowpathway is sliced open. These techniques share in common blunt manualdissection of an area that is mere microns in dimension.

Thermal lasers have also been used to surgically manipulate the ocularoutflow pathway. These are known as laser trabeculoplasty and use thelaser to heat the entrance of the ocular outflow pathway (trabecularmeshwork). Typically, the surgeon uses a single faceted mirror to seeone area of the trabecular meshwork and apply the laser, thecircumferential extent is treated by physically spinning the facet toaccess the remaining areas. This treatment is primarily superficial;involvement of deeper structures is usually a result of inadvertentthermal/biological changes from the superficial laser treatment.

In an ideal scenario, the precision of the laser would be used totherapeutically change the deeper structures of the ocular outflowpathway. In contrast to “scalpel surgery,” this would provide aminimally invasive targeted means of altering any pathologic areas ofthe outflow pathway.

With an optical system that allows for direct OCT viewing of the ocularoutflow pathway from inside the eye to create tomographic images of thisarea, one would have the ability to visualize the pertinent structures.Because OCT is an optical technique, laser energy can also be deliveredvia the same optical system. In this way, minimally invasive,image-guided therapeutics of the ocular outflow tract become possible.

Thus, improved optical access to structures of the eye would improvediagnosis and treatment of conditions related to structures inside theeye, especially peripheral structures that have heretofore beendifficult to access by direct imaging methods.

SUMMARY

In one embodiment, the invention provides a system for obtaininglow-angle circumferential optical access to an eye of a subject. Thesystem includes a light source to generate a beam of light; a beamsteering mechanism to steer the beam of light a focusing lens to focusthe beam of light; and a contact lens to direct the beam of light intothe eye of the subject, the contact lens including a tapered reflectivesurface to direct the beam of light into the eye of the subject.

In another embodiment the invention provides a method for obtaininglow-angle circumferential optical access to an eye of a subject. Themethod includes steps of generating a beam of light using a lightsource; steering the beam of light using a beam steering mechanism;focusing the beam of light using a focusing lens; and directing the beamof light into the eye of the subject using a contact lens, wherein thecontact lens includes a tapered reflective surface to direct the beam oflight into the eye of the subject.

In yet another embodiment, the invention provides a contact lens forobtaining low-angle circumferential optical access to an eye of asubject. The contact lens includes an optically transparent body havinga tapered reflective surface; an eye contacting portion at a first endof the body; and a light entry portion at a second end of the body.

Other aspects of the invention will become apparent by consideration ofthe detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a ZEMAX ray trace diagram showing three basic elements of alow-angle circumferential optical access system including a beamsteering mechanism, a focusing lens, and a contact lens.

FIG. 2 shows a high-level diagram of a spectral domain implementation ofgonioscopic OCT.

FIG. 3 shows a close-up view of the interface between a contact lens andthe cornea of a subject, including a ray-trace showing the path of lightreflecting off the tapered surface of the contact lens and crossing intothe cornea through a coupling fluid.

FIG. 4A shows the appearance of the iris, pupil, sclera, andirid-corneal angle in the eye of a subject.

FIG. 4B shows a circumferential-priority scan pattern in which only arepresentative number of scans is shown.

FIG. 4C shows a radial-priority scan pattern in which only arepresentative number of scans is shown.

FIG. 5 shows several screenshots of a clinical data analysis system.

FIG. 6 shows an embodiment of a system for obtaining low-anglecircumferential optical access to an eye of a subject.

FIGS. 7A-7F show an embodiment of a contact lens for obtaining low-anglecircumferential optical access to an eye of a subject; FIG. 7A is afront view, FIG. 7B is a side view, FIG. 7C is a rear view, FIG. 7D is across-sectional view through the line B-B shown in FIG. 7E, FIG. 7E isanother side view, and FIG. 7F is a close-up view of the asphericannular surface.

FIG. 8 shows a contact lens having a frustoconical reflective surfaceand a hemitoroidal refractive surface at the point of light entry.

FIG. 9 shows a gonioscopic bore which allows for fine control ofastigmatism correction.

FIG. 10 shows a bore attached to a hand held probe.

DETAILED DESCRIPTION

Before any embodiments of the invention are explained in detail, it isto be understood that the invention is not limited in its application tothe details of construction and the arrangement of components set forthin the following description or illustrated in the following drawings.The invention is capable of other embodiments and of being practiced orof being carried out in various ways.

The present disclosure provides in part an optical system along withmethods that allow for OCT viewing of the ocular outflow pathway frominside the eye to create tomographic images of this area and other areasof the eye. This optical system also allows for full circumferentialscanning of the outflow pathway. The optical system can be built eitheras an add-on accessory to existing commercially-available retinal oranterior segment OCT systems, or can be built as a standalone handheldor portable system. Additionally, methods to analyze and present theseimages for clinical use are provided. As this system is based on OCT,previously-developed functional OCT techniques such as Doppler orelastography can further extend the platform to allow characterizationof flow and resistance through this pathway.

One aspect of the present disclosure provides a system which includes anoptical arrangement for delivering a tightly-focused OCT beam from aconventional OCT x-y scan head through the cornea and into theirido-corneal angle in a fully circumferential scannable geometry. Tooptically image the internal entrance of the ocular outflow pathwaythrough the clear central cornea, one must account for total internalreflection due to the required steep angle of approach and the largeindex change at the air-cornea interface. Collimated OCT light isdirected towards the cornea as in conventional anterior segment OCT.However, a custom focusing contact lens system is introduced to redirectand focus OCT light into the ocular outflow pathway. By placing thiscontact lens system on the cornea (and directly coupling the contactlens to the patient's eye using a balanced salt solution or similarsolution), the large air-cornea index change is eliminated as the indexchange is greatly reduced, being between several materials havingsimilar indices of refraction, namely the contact lens system, thecornea, and the salt solution. In some embodiments, the saline solutionmay include so-called ‘gel’ eye drops which have a lubricant such ascarboxymethyl cellulose, hydroxypropyl methyl cellulose, hydroxypropylcellulose, hyaluronic acid, or other similar polymers found inartificial tears, gels, or ointments.

To obtain continuous scanning around the entire ocular outflow pathway,which has a circular geometry, and to achieve the steep angle ofapproach required to observe the pathway, the resulting geometry for acontact lens reflector in various embodiments includes a taperedsurface. The tapered surface of the contact lens may have a straight orcurved profile, or combinations of different profile shapes and angles,and may include frustoconical and/or parabolic shapes.

For the straight-profile frustoconical shape, each point along thesurface varies in positive focusing power depending of the radius of thecone at the incident position of the beam. This positive focusing,however, occurs only in a single dimension, resulting in an astigmatismwhose angle is dependent on the azimuthal angle of the cone on which thebeam is incident. Thus, in one embodiment, to correct for theseastigmatisms, a second cone that has negative focusing power can beplaced in front of the reflective cone (FIG. 1). This combination of twoconical shapes for directing the beam of light to the eye generallyreduces the overall error due to astigmatism.

In other embodiments including those described further below, instead ofa negative focusing power cone, the point of light entry on the contactlens includes a convex surface through which the beam of light entersthe contact lens. The convex surface in one particular embodiment is ahemitoroidal projection (FIG. 8). In another embodiment, the point oflight entry is an annular aspheric surface (FIGS. 7A-7F).

Another aspect of the present disclosure provides methods for scanningthe OCT beam in an efficient manner, e.g. in radial-priority orcircumferential-priority, to generate useful clinical output in minimumimaging time. In various embodiments, the beam of light is moved using abeam-steering mechanism (e.g. galvanometers or other mechanisms) toreach a particular location on the eye. An A-scan is obtained at thelocation (to provide depth information), after which the beam is movedto another location to obtain another A-scan, a procedure that isrepeated for a series of locations of the eye. The information from aplurality of A-scans is then combined to generate an image or portion ofan image. The beam may be scanned in a number of different patterns,including radial or circumferential, which may encompass varyingportions of the eye. In some embodiments, data may be collected from theentire circumference of the eye and in other embodiments data may onlybe collected from a portion or portions of the eye, for example a regionof particular interest for diagnosis and/or treatment of a patient.

The outflow pathway may be scanned with circumferential or radial (i.e.cornea to iris) priority to create a given B-scan. Subsequent B-scansmay be scanned in the other direction (radial or circumferentially) tocreate a tomographic volumetric representation of the ocular outflowpathway.

Other embodiments of the present disclosure provides methods forsegmenting, processing, and displaying the resulting image dataset in away most readily understandable and useful to clinicians. The collectedimages are segmented using methods such as intensity segmentation, graphtechniques with dynamic programming, or others to identify regions ofinterest including the trabecular meshwork (TM) and Schlemm's canal(SC). Morphometric parameters that have histologically been correlatedwith glaucoma (e.g. thickness of the TM and size of the SC) can then bedisplayed either directly or symbolically for clinical interpretation.Additional parameters depending on the OCT technique used can also beshown similarly (flow, elastography). In various embodiments, inaddition to the optical system for circumferential scanning of theocular outflow pathway to provide diagnostic images, the system alsoincludes an optical system for delivering therapeutic light, for exampleusing a laser platform.

The optical system according to one embodiment of the presentdisclosure, which is based on scanning a single spot around the ocularoutflow pathway, includes three distinct components. The firstcomponent, the beam steering mechanism, provides the ability to scan asingle beam of collimated light in two dimensions. The second component,the focusing lens, is the need to focus the collimated beam after thescanning of the beam. The final component, provided by the contact lens,achieves the steep angle required to observe the ocular outflow pathway.Any or all of these components could potentially be combined to achievethe desired results. A high-level schematic of a spectral domainimplementation of gonioscopic OCT is shown below in FIG. 2, although inother embodiments gonioscopic OCT can be extended to any OCTimplementation (including time domain and Fourier domain OCT).

FIG. 1 shows an embodiment of an optical system including a contact lensfor obtaining low-angle circumferential optical access to an eye of asubject. For simplicity, in the design of FIG. 1, each component isdepicted as a separate optical device. Nevertheless, the simplifiedsystem of FIG. 1 could be expanded with a more complex system of lensesand other components and/or through the use of focusing mirrors.

The optical system includes a beam steering mechanism (shownschematically on the left side of FIG. 1) having a pair of mirrorsmounted on orthogonal axis galvanometers. In other embodiments, the beamsteering mechanism may include, but is not limited to, mirrors that canpivot in two axes, rotating prism pairs, acousto-optic deflectors,resonant scanning mirrors, rotating polygonal scanning mirrors, andmicroelectromechanical system (MEMS) based scanning devices.

The focusing objective depicted in FIG. 1 may be a single radiallysymmetric achromatic lens which provides the entirety of the necessaryfocusing power of the system, or this functionality may be provided bytwo or more focusing lenses.

The final element of the system requires a method to achieve the steepangle of incidence required for imaging the outflow pathway. Thisunfortunately cannot be done using a simple air-to-cornea interface dueto total internal reflection and therefore requires an adapter. In thesystem shown in FIG. 1, this adapter or contact lens has a single pieceof poly(methyl methacrylate) (also known as PMMA or acrylic) coupled tothe cornea with balanced salt solution or other similar compound(s).PMMA was chosen as the material for many reasons including better indexmatching between contact and cornea than most types of glass, ease ofmanufacturing, high Abbe number (which relates to a low chromaticdispersion value), and because the material is strong and lightweight.Nevertheless, in some embodiments other materials such as glass may beused. In one embodiment, N-FK51A (Schott) glass is used, allowing forlower chromatic dispersion. In other embodiments, the contact lens maybe made using a plastic such as Zeonex E48R or inorganic crystals suchas calcium fluoride (CaF₂)

In the contact lens shown in FIG. 1 has several unique features, thebeam entrance consists of a negative cone (or axicon) shape. This shapehelps to steer the beam at a steep angle away from the optical axis andalso provides negative astigmatism compared to a flat entrance; thisastigmatism is dependent on both distance from the cone apex and theradial angle of the beam entrance. Once the beam has entered the PMMA,it is angled such that when it hits the next surface, it does so atgreater than the critical angle resulting in total internal reflection.Using this reflection negates the need for a metal mirror as a reflectorto achieve the desired steep incidence angle for imaging the ocularoutflow pathway. Nonetheless, in various embodiments, the taperedreflective surface of the contact lens may be coated with a reflectivematerial including a metal such as gold, silver, aluminum, or adielectric material to improve reflectivity.

The contact lens also includes at one end a concave surface or well forplacement of the subject's cornea along with the coupling solution. Inone embodiment the concave surface has a spherical radius of curvatureof 7.4 mm to match that of typical corneas. In other embodiments, theconcave surface may have other sizes and shapes to accommodate varioussubjects' corneas. In various embodiments, the region of the contactlens outside of the concave well includes a lip to provide mechanicalsupport and stabilization such that sliding of the contact is minimizedduring image acquisition. A ray trace diagram showing in detail thereflection from the tapered reflective surface (including the totalinternal reflection) within a contact lens made of PMMA as well as theeffect of the index matching between the contact and cornea is shown inFIG. 3.

Given an optical system which delivers a tightly focused, scannable spotthrough the transparent cornea into the irido-corneal from the inside ofthe eye, as described above, this optical system can be utilized toperform tomographic scanning of the outflow pathway within the angleregion with optimal coverage (not missing any critical structures) andefficiency (scan time).

Two basic scan patterns for examining the outflow pathway from insidethe eye are disclosed in FIG. 4. Both scan patterns are defined withrespect to standard OCT imaging terminology, wherein an A-scanrepresents a single depth-resolved axial reflectivity map, a B-scangenerally refers to a two-dimensional cross-sectional image constructedfrom a series (typically 100-1000) of laterally-displaced A-scans whichcan be viewed as an image, and a volume scan represents athree-dimensional dataset typically constructed from a sequence(typically 100-1000) of azimuthally displaced B-scans. FIG. 4A shows thestructures of the eye of a subject. The circumferential-priority scanpattern, illustrated in FIG. 4B, is comprised of one or more B-scansobtained while scanning the focused spot in a circular pattern aroundthe circumference of the irido-corneal angle. If the subject's eyeremains sufficiently stationary, a single or a few sequentialcircumferential B-scans may be positioned to view the entirecircumference of circular structures such as Schlemm's canal. Morepractically, a series (10-1000) of sequential circumferential-priorityscans with different radii may be obtained in order to collect a volumeof data including all relevant outflow structures. The advantages ofcircumferential-priority scanning include maximum continuity of imageintegrity for circular structures; however, the primary drawback of thisscan pattern lies in its sensitivity to patient motion.

An alternative scan pattern is the radial or partial radial scan patternillustrated in FIG. 4C. In this pattern, a sequence of one or morerelatively short radially oriented B-scans are obtained in a circularpattern around the circumference of the irido-corneal angle. Theindividual radial B-scans may extend all of the way to the center ofcornea, as in a conventional radial OCT scan pattern; however, thepattern will be more efficient if only the relevant parts of the radialprofiles are scanned. The principle advantage of the radial scan patternis that local segments of the irido-corneal tomographic data sets willbe relatively free of motion artifacts since they are acquired in rapidsequence.

Once the images are acquired, regions of clinical interest may beidentified and displayed for clinical interpretation. For illustrativepurposes, morphometric analysis of Schlemm's canal will be describedhere, as dimensions of this canal have been correlated with glaucoma inhistologic studies. However, other anatomic components of the outflowpathway including but not limited to trabecular meshwork and itssubcomponents, collector channels, and distal vessels may also be imagedand treated similarly as in this illustrative example. Analyses also donot have to be limited to morphometric examination; functionalinvestigations available on the OCT platform can be made available tothe trabecular meshwork with this design.

For morphometric analysis of Schlemm's canal, the structure is firstidentified. Anatomically, Schlemm's canal is located distal to thetrabecular meshwork (where proximal is the anterior chamber and thesuperficial cornea is distal to Schlemm's canal). Because of thisrelationship to the trabecular meshwork, the search region can belimited to the termination of Descemet's membrane anteriorly and theiris root posteriorly, both identifiable structures on OCT.

In this region, Schlemm's canal is seen as a hyporeflective area in OCTas it is a fluid-filled structure, in contrast to the surroundingtissue. Using desired manual and/or automated image processingsegmentation techniques (e.g. threshold, graph cut, edge detection,region growing, and others) including any requisite preprocessing,Schlemm's canal is identified in each individual image of the volumetricacquisition.

Once identified, Schlemm's canal is removed from the surrounding imageand can simply be displayed in isolation three-dimensionally. To improvethe clinical utility of this information, though, dimensions of thecanal can be extracted and morphometric parameters computed. Theseparameters can be local, e.g. diameters at various locations around thecanal, as well as global, e.g. volume of the entire canal. Themorphometric parameter can then be compared to a reference value such asthe canal maximum or against a normative database.

FIG. 5 shows a sample output from an OCT scan of the outflow pathwayhighlighting Schlemm's canal, presented as a series of screenshots. Ineach screenshot, the acquired image is on the left. On the right is asymbolic map showing the location of the image along the circumferenceof the canal. The area of the canal in that particular “slice” of thecanal is displayed underneath the image. The symbolic map also colorcodes this area as compared against the canal maximum. In thisparticular example, yellow means the area is <50% of the canal maximumand red means the area is <25% of the canal maximum. Using an overlay,the segmented Schlemm's canal can also be shown to the user. With thisdisplay, the captured image is readily available to the clinician, butfor ease of use, the symbolic map also quickly signals to the clinicianthe areas which may be pathologic. In this particular example, a surgeonplanning on inserting an outflow bypass device can now know which areasof the canal are likely nonfunctional and will likely benefit from thebypass (versus the current standard of simply placing it in a randomquadrant).

Similar segmentations, analyses, and displays can also be performed forother ocular outflow substructures and gonioscope OCT data. Multipleanalyses could also be displayed in a single screen (adding anotherconcentric circle to the above symbolic map indicating trabecularmeshwork thickness, for example).

Yet another aspect of the present disclosure provides a device andsystem that incorporates a continuous scan circular mirror. Such asystem includes an optical system for circumferential scanning of theocular outflow pathway to provide diagnostic images and a therapeuticlaser platform. One embodiment provides for a combination of thecircumferential scanning optical system described herein for opticalcoherence tomography (OTC) imaging along with an ophthalmic femtosecondlaser. The ophthalmic femtosecond laser in one embodiment may be aninfrared laser (˜1040 nm) that creates precise cleavage planes intissues via photodisruption. Currently, it is used for creating corneallamellar flaps at desired depths as would be used in laser refractivesurgery.

In one embodiment, the optical system is applied to the eye and acircumferentially scanned OCT image is obtained of the ocular outflowpathway. As the site of ocular outflow resistance is thought to be atthe interface between the trabecular meshwork (TM) and Schlemm's canal(SC), this region would be identified in the image either manually orautomatically. Using this image guidance, the ophthalmic femtosecondlaser would then be used to open the TM-SC interface circumferentiallyaround the eye by focusing therapeutic laser energy in that specificregion via the same optical system used to deliver infrared OCT lightfor diagnostic purposes. OCT imaging can be used in a concurrent,interlaced fashion or sequentially to monitor the progress of thetherapeutic laser. By precisely removing the TM-SC interface, the majorsite of ocular outflow resistance can be eliminated without disruptingsurrounding tissues as would occur with a manual blade or currenttrabeculoplasty lasers.

FIG. 6 depicts another embodiment of a system 100 for obtaininglow-angle circumferential optical access to an eye of a subject. Thesystem includes a light source 110 and a fiber coupler 120. In thedepicted embodiment, the fiber coupler 120 splits the light from thelight source 110 and sends a portion to a reference arm and anotherportion to a sample arm as part of an OCT system. The reference arm ofthe depicted embodiment includes a polarization controller 130, acollimating lens 140, a dispersion compensating cube 150, an achromaticlens par/focusing lens pair 160, and a reference mirror 170. The samplearm includes a collimating lens 180, a dichroic mirror 190, a beamsteering mechanism 200 (which may include a galvanometer pair as shown),an achromatic lens par/focusing lens pair 210, and a contact lens 220.The depicted embodiment of the system 100 also includes an iris camera230 and white light source 240, along with suitable optical components,to be used as part of an alignment system. The light source 110 caninclude a swept-source OCT (SSOCT) laser centered at λ=1050 nm with Δλ,=100 nm, although other types of sources are also possible. In someembodiments, the light source 110 may include any spatially coherentbroadband visible or near-infrared light source operated with an axialscan rate from 10 Hz to 10 MHz, where the bandwidth may vary from 10 nmto hundreds of nanometers. In other embodiments, the light source 110may include superluminecent diodes having center wavelengths includingbut not limited to 830 nm, 1050 nm and 1310 nm. In yet otherembodiments, the light source 110 may include a Fourier-domain modelocked (FDML) laser having a center wavelength such as 1050 nm or 1310nm. In still other embodiments, the light source 110 may include avertical-cavity surface-emitting laser (VCSEL) having a centerwavelength such as 1050 nm or 1310 nm. In further embodiments, the lightsource 110 may include a femtosecond laser such as a titanium-sapphire(Ti—AlO₃) laser or a supercontinuum laser. The center wavelengths mayvary from the stated center wavelength values, for example in certainembodiments by approximately ±40 nm for at least some of the lightsources 110 listed above.

Also coupled to the fiber coupler 120 is a photo detector 250 which inturn is connected to an acquisition and processing computing system 260.In certain embodiments, the photo detector 250 collects light from aseries of A-scans which contain depth information for a given point onthe sample and this A-scan information from several points on the sampleis then processed by the acquisition and processing computing system 260to produce images. The images are then analyzed, stored, and/ordisplayed to a user.

An additional feature of the depicted system 100 is a therapeutic lightdelivery arm, which in the depicted embodiment includes a light source270, e.g. a 532 nm laser source, and suitable optical couplingcomponents 280, e.g. a collimating lens, for tissue ablation and othertreatments. The therapeutic light source 270 may include lasers or otherlight sources in the UV, visible, or infrared portions of the spectrum.

Subjects may include humans and other primates as well as laboratoryresearch subjects such as mice, rats, and rabbits. Embodiments of thedisclosed system 100 can be used to view and/or treat structures of theeye that are difficult or impossible to access using other techniques,including the iridocorneal angle and peripheral regions of the retina.

FIGS. 7A-7F show an embodiment of a contact lens 220 for use with thesystem 100. As discussed above, the contact lens 220 may be fabricatedfrom a number of optically transparent materials including glass orPMMA. The contact lens 220 includes a tapered reflective surface 222which may be a composite having several segments each with a differentshape (e.g. parabolic or frustoconical) and/or taper angle; in theembodiment shown in FIGS. 7A-7F, the reflective surface 222 has aparabolic cross section.

The front surface of the contact lens 220 includes an aspheric annularsurface 226 (FIG. 7F) through which light enters the contact lens 220.The aspheric annular surface 226 corrects for the astigmatism wouldotherwise be introduced by the parabolic reflective surface 222. Incertain embodiments, all or a portion (e.g. the aspheric annular surface226) of the front surface of the contact lens 220 may be coated with anantireflective coating. As discussed above, the reflective surface 222may have a reflective coating applied thereto.

The contact lens 220 includes a concave surface 224 to fit into thecornea of the eye of the subject. The concave surface 224 can havevarious sizes and shapes to accommodate various subjects' corneas. Thecontact lens 220 can also include an outer rim 228 for mounting, e.g. toa bore.

FIG. 8 shows an embodiment of a contact lens having a frustoconicalreflective surface and where the front surface includes a hemitoroidalrefractive surface which corrects for the astigmatism introduced by thefrustoconical reflective surface. FIG. 9 shows a gonioscopic bore,including a focusing lens pair and a contact lens, which allows for finecontrol of astigmatism correction by facilitating fine control of thedistance between the focusing lenses and the contact lens, which in turnadjusts the imaging properties of the contact lens. FIG. 10 shows a boresuch as that shown in FIG. 9 attached to a hand held probe.

Thus, the invention provides, among other things, methods and systemsfor obtaining low-angle circumferential optical access to the eye.Various features and advantages of the invention are set forth in thefollowing claims.

What is claimed is:
 1. A method for obtaining low-angle circumferentialoptical access to an eye of a subject, the method comprising the stepsof: generating a beam of light using a light source; steering the beamof light using a beam steering mechanism; focusing the beam of lightusing a focusing lens; and directing the beam of light into the eye ofthe subject using a contact lens, wherein the contact lens includes atapered reflective surface to direct the beam of light into the eye ofthe subject, and wherein the tapered reflective surface includes aplurality of sections having different angles of taper.
 2. The method ofclaim 1, further comprising detecting light reflected from the eye ofthe subject using a detector.
 3. The method of claim 1, wherein thecontact lens further comprises a convex surface through which the beamof light enters the contact lens.
 4. The method of claim 1, wherein theconvex surface comprises an annular aspheric surface at the perimeter ofthe contact lens through which the beam of light enters the contactlens.
 5. The method of claim 1, wherein the tapered reflective surfaceis radially symmetric about a central axis, wherein the beam of lightextends from the focusing lens to the contact lens, and wherein thetapered reflective surface directs the beam of light towards the centralaxis and into the eye of the subject.
 6. The method of claim 1, whereinthe contact lens comprises an optically transparent material and whereinthe tapered reflective surface of the contact lens has a reflectivematerial applied thereto.
 7. The method of claim 1, wherein the beamsteering mechanism comprises at least one galvanometer.
 8. The method ofclaim 1, wherein the focusing lens comprises a focusing lens pair. 9.The method of claim 1, wherein directing the beam of light into the eyeof the subject further comprises directing the beam of light into theiridocorneal angle of the eye of the subject.
 10. The method of claim 1,further comprising coupling the contact lens to the eye of the subjectusing a saline solution.
 11. The method of claim 1, further comprisinggenerating a beam of therapeutic light using a therapeutic light sourceand directing the beam of therapeutic light through the contact lensinto the eye of the subject.
 12. The method of claim 1, wherein thelight source comprises a therapeutic light source.
 13. The method ofclaim 1, wherein the tapered reflective surface has a shape selectedfrom frustoconical and parabolic.
 14. The method of claim 1, whereingenerating a beam of light further comprises dividing the beam of lightinto a sample arm and a reference arm, directing the sample arm to thebeam steering mechanism, and directing the reference arm to a referencemirror.
 15. The method of claim 14, further comprising receiving lightreturned from the sample arm, receiving light returned from thereference arm, and combining the light from the sample arm with lightfrom the reference arm to produce an interference signal.
 16. The methodof claim 15, further comprising detecting the interference signal withthe detector.
 17. The method of claim 15, further comprising combiningthe interference signal from a plurality of locations on the eye of thesubject to produce at least one image.
 18. A contact lens for obtaininglow-angle circumferential optical access to an eye of a subject, thecontact lens comprising: an optically transparent body comprising atapered reflective surface; an eye contacting portion at a first end ofthe body; and a light entry portion at a second end of the body, whereinthe tapered reflective surface comprises a plurality of sections havingdifferent angles of taper.
 19. The contact lens of claim 18, wherein thetapered reflective surface is adjacent to the eye contacting portion.20. The contact lens of claim 18, wherein the tapered reflective surfacecomprises a frustoconical portion.
 21. The contact lens of claim 18,wherein the tapered reflective surface further comprises a parabolicportion.
 22. The contact lens of claim 18, wherein the eye contactingportion comprises a concave surface.
 23. The contact lens of claim 18,wherein the light entry portion comprises an anti-reflective coating.24. The contact lens of claim 18, wherein the light entry portioncomprises an annular aspheric surface.
 25. A method for obtaininglow-angle circumferential optical access to an eye of a subject, themethod comprising: generating a beam of light using a light source; andsteering the beam of light using a beam steering mechanism to direct thebeam of light onto a refractive surface of a contact lens, wherein therefractive surface is shaped to refract the beam of light entering thecontact lens through the refractive surface at an angle away from acentral axis of the contact lens and towards a tapered reflectivesurface of the contact lens, and wherein the tapered reflective surfaceis radially symmetric about the central axis and is shaped to reflectthe refracted beam of light towards the central axis and into the eye ofthe subject.
 26. The method of claim 25, further comprising operatingthe steering mechanism to adjust a steered position of the beam of lightrelative to the refractive surface of the contact lens to obtaincircumferential optical access.